Does Case Length Matter?

Greetings,

Fascinated by the topic of "Does Case Length Matter" I conducted a test to see "what if".

I used a box of gifted 68BB 204 grain clone bullets gifted to me. They were sized 0.453" with a Red Lube. I sorted out the ones with fewest "dings".

Brass was StarLine sized to 0.469" diameter.

Primers were some CCI 300 I had in the back of the cabinet.

Fifty rounds each were loaded with cases 0.893", 0.888", and 0.886".

4.0 grains of current Bullseye was the charge.

Seating depth was 1.240".

0.465" Taper Crimp.


The barrel used was a 5" Kart commercial and the head space was 0.892".

Chamber was a minimum dimension SAAMI spec.


Mounting the barrel in a test fixture, I fired five ten shot groups with each length starting with the 0.893", next, 0.888", finally, the 0.886".

I did dry brush the barrel between 50 shot events.


After collection, scanning, and analyzing the test targets, I could not see any appreciable difference in the Mean Radius of the groups.

Most groups were 8-9 X targets with a flier. The flier I attributed to being a "bad" bullet.

A few days later, a light came on between my ears. When I was testing, I noticed that the bolt did not close on the ammunition with ease. There was a slight amount of "crush" to seat the cartridge so that the bolt was in contact with the barrel hood.

Finally, it came back to me. Years ago, before custom National Match barrels, the barrel hoods were welded up and cut to fit the slide. This resulted in a LONG head space. To compensate for this we seated the bullets out longer to engage the Leade of the throat resulting in a sort of ZERO head space.

In summary, my test has been somewhat invalid. The cases were never engaging the head space shelf of the chamber. Caveat, the 0.893" cases would have had to engage the chamber shelf. Still, all the cartridges were the same length from base to bullet shoulder and a slight "crush" was needed to seat them.

If you want to see the targets, send me an email and I will reply with the scanned and analyzed results your way.

Cheers,

Dave,  RCB

If you’re up to a re-do, seat the bullets to shoulder of .898.  But I’m not sure if you’d ever get reasonable results … or shoot JHP.  

I’d like to have the data and photos, please.

Dave, your 888 ammo should command a huge premium if sold to folks of Cantonese origin - just sayin'.

Dave if all your test rounds had the same overall length doesn't that mean that all your cases had the same internal space? It wouldn't mater what the case length is. In the world outside barrel fixtures the longer cases would headspace off the heads pace shelf and the shorter cases would headspace off the extractor. Either way you should get very similar results. I've never measured  nor sorted my empty brass (except by headstamp). I do try very hard to make my overall length consistent. An interesting test would be testing .893 and .870 with same crimp. If possible..

LenV wrote:Dave if all your test rounds had the same overall length doesn't that mean that all your cases had the same internal space? It wouldn't mater what the case length is. In the world outside barrel fixtures the longer cases would headspace off the heads pace shelf and the shorter cases would headspace off the extractor. Either way you should get very similar results. I've never measured  nor sorted my empty brass (except by headstamp). I do try very hard to make my overall length consistent. An interesting test would be testing .893 and .870 with same crimp. If possible..

Greetings Len,

With the same brand of cases, I would expect the internal space to be equal.

The chronograph showed little difference in velocity between the three case lengths.

Taper crimping was brought about to deal with cases of varying length.

Cheers,

Dave

I think I got a timeout the last time I commented on this topic.

So does your test imply that case length differences can be mitigated by seating depth? At least thats what my tired mind seems to interpret

This - seated the bullets out longer to engage the Leade of the throat resulting in a sort of ZERO head space.


Its in an old NRA reprint of the 45acp.  Best for slow fire accuracy. 
Removes end play. 

[quote="john bickar"]I think I got a timeout the last time I commented on this topic. :lol:[/quote]


Hmmmm.  I wonder if this has anything to do with the influence of the extractor?????   :lol: :lol:

fc60 wrote:Finally, it came back to me. Years ago, before custom National Match barrels, the barrel hoods were welded up and cut to fit the slide. This resulted in a LONG head space. To compensate for this we seated the bullets out longer to engage the Leade of the throat resulting in a sort of ZERO head space.

I recall reading about that as being the "correct" way to seat LSWC projectiles when I first began reloading. I did do it that way for a while and then began shooting different guns, so landed on a common length to suit all.

I may try that again now that I am loading for only two 1911's and do a comparison.

If you do a re-test of the above it will be interesting to see the results above compared to the results of your next test when headspacing off of the case mouth.

Thank you for all of the research you take the time to do and share!!

inthebeech wrote:

john bickar wrote:I think I got a timeout the last time I commented on this topic.

Hmmmm.  I wonder if this has anything to do with the influence of the extractor?????  

Grrrreetings,

Interesting comment.

The extractor, if not properly fitted, could have an influence on the cartridge positioning. (Applies to Bottom Feeders only.)

Fortunately, I shoot a revolver and only have to deal with Moon Clips.

Cheers,

Dave

john bickar wrote:I think I got a timeout the last time I commented on this topic.

Grrrreetings Young John,

Please post your comments.

I await your views/opinions with the greatest anticipation.

Cheers,

Dave,  RCB

“ There was a slight amount of "crush" to seat the cartridge

Hello Dave, first thank you as always for the testing you do.  It’s awesome to be on this forum and get to read your posts. Shows me how little I actually know and that most of what I think I know is not from actual experiments. 

Question, when you mention a “crush” are you saying that the bullet shoulder was contacting the end of the chamber and the bullet was getting squished (or even seated deeper)?  What do you think that means at the end of the day?

Many Thanks again!

RodJ wrote:“ There was a slight amount of "crush" to seat the cartridge

Hello Dave, first thank you as always for the testing you do.  It’s awesome to be on this forum and get to read your posts. Shows me how little I actually know and that most of what I think I know is not from actual experiments. 

Question, when you mention a “crush” are you saying that the bullet shoulder was contacting the end of the chamber and the bullet was getting squished (or even seated deeper)?  What do you think that means at the end of the day?

Many Thanks again!

Grrrreetings Rod,

By "crush" I mean the shoulder of the bullet is being forced into the Leade of the chamber.

With the 0.465" Taper Crimp I doubt the bullet was pushed back into the case. One reason the Taper Crimp came to being.

At the end of the Day?  If you start getting malfunctions, slide does not close fully, you will likely start seating the bullets deeper to avoid this issue.

I have been testing barrels from several manufacturers. The chambers vary in dimension greatly. What may be a "crush" fit with one barrel may be an easy fit with another.

Cheers,

Dave

If I read correctly, we're discussing, to stretch the term, headspacing off the bullet.

In which case the importance of the case length may be hidden?

If the case head spaces on the case mouth, the case should match the head space. Trimming cases like 9x19 or 45Auto is a waste of time and hurts accuracy.
Accuracy is best minimizing head space gap.

Another anecdotal result.  It’s long been  true that one of the most accurate ammo has been the Atlanta Arms 185Jhp.  It’s loaded to 1.235 inches.  I don’t know if there’s enough bullet sticking out to “crush” but I seriously doubt it.  So there’s no headspacing on the bullet.  Yet it shoots very well.   Maybe case length isn’t that important. 

Wobbley wrote:Another anecdotal result.  It’s long been  true that one of the most accurate ammo has been the Atlanta Arms 185Jhp.  It’s loaded to 1.235 inches.  I don’t know if there’s enough bullet sticking out to “crush” but I seriously doubt it.  So there’s no headspacing on the bullet.  Yet it shoots very well.   Maybe case length isn’t that important. 

Those are made with new Starline brass, so likely 0.892 - 0.893"-ish cases.

I wet tumble new Starline to deburr the case mouths and then sort by length, so I see few at above 0.893" length. I measure twice at 90 degrees apart and sort by lowest measurement.

Wobbley wrote:Another anecdotal result.  It’s long been  true that one of the most accurate ammo has been the Atlanta Arms 185Jhp.  It’s loaded to 1.235 inches.  I don’t know if there’s enough bullet sticking out to “crush” but I seriously doubt it.  So there’s no headspacing on the bullet.  Yet it shoots very well.   Maybe case length isn’t that important.

Grrreetings,

Here, it varies with the way your barrel is chambered.

I tested some ZERO, ASYM, and Atlanta Arms ammo for a fellow shooter and some of the new, never fit, barrels I have the ammo sticks in the leade of the chamber. Other barrels it drops in and drops out.

Cheers,

Dave

A friend of mine would look at my loads and say they were too long and I should seat the bullets deeper. I saved a few of the long ones and when I got home, I pulled my barrel and did the plunk test to check them for overall length. 
I found they were flush with the barrel hood and not too long. So, I started measuring my brass for length to make more consistent loads. 
To be honest I couldn't see any difference in accuracy, but they looked better in appearance. 
My biggest problem is still having the bullets creep back out of the case after seating them do to the air not escaping when seating long waisted bullets like the 185gr Zero LSWCHP and the 200gr 130 H&G. I have a flat base PTU in my powder measure and seems to expand the case too deep when I set it to bell the case mouth just enough to start the bullets by hand.
I have run cases through the PTU without dropping any powder to check the expanding depth by hand and can visually see that the case mouth is not touching the belling portion of the PTU. The only thing I can figure is the bullet lube is causing a seal that traps the air while seating the bullet and then pushing the bullet back out.
I have a spare barrel that has the same chamber dimensions and use it to check the overall length of my loads. I drop each one in the barrel after cleaning off any excess lube and brass flakes that sticks to the cases.

Sometimes goop in the seater die results in the bullet being pulled back out…